Efficiency optimizer of an audio power amplifier for car radio

Abstract

The present invention concerns an audio amplifier circuit designed to provide an output signal to an audio transducer, said audio amplifier circuit comprising an audio power amplifier designed to receive an audio signal and designed to generate said output signal, a sensor designed to detect an audible sound having at least one noise component, to generate a detected signal. The audio amplifier circuit also includes a processing block configured to receive said detected signal at its input and to generate an off signal at its output, the latter being located at the input of said audio power amplifier. The processing block processes the detected signal according to said input signal to identify said noise component of said detected signal to generate a reference signal. The processing block generates the off signal when the value of said input signal is lower than the value of said reference signal.

The invention claimed is: 
     
       1. An audio amplifier circuit configured to provide an output signal to an audio transducer, said audio amplifier circuit comprising:
 an audio power amplifier having first and second inputs and an output, the audio power amplifier being configured to receive an audio signal at the first input and generate said output signal at the output; 
 an audio sensor configured to detect an audible sound, said audible sound having a noise component, said audio sensor being configured to generate a detected signal; and 
 a processing block circuit configured to receive said detected signal, generate an off signal, and provide the off signal to the second input of said audio power amplifier, said processing block circuit being configured to identify said noise component of said detected signal and generate a reference signal by processing said detected signal according to said input signal, said processing block circuit also being configured to generate said off signal when a value of said input signal is lower than a value of said reference signal. 
 
     
     
       2. An audio amplifier circuit as claimed in  claim 1 , wherein said processing block circuit is configured to generate said off signal if, during at least a first period of time ranging from 70 msec to 130 msec, the value of said first input signal is lower than or equal to the value of said reference signal. 
     
     
       3. An audio amplifier circuit as claimed in  claim 1 , wherein said processing block circuit comprises an adaptive filter block circuit configured to filter said input signal according to said detected signal, reduce a mean-square error, and generate a filtered signal. 
     
     
       4. An audio amplifier circuit as claimed in  claim 3 , wherein said processing block circuit comprises an amplitude determining block circuit configured to receive said filtered signal and generate a modulus signal representative of an amplitude value of said filtered signal. 
     
     
       5. An audio amplifier circuit as claimed in  claim 4 , wherein said processing block circuit comprises an on/off block circuit configured to receive said modulus signal generate said off signal and process said reference signal by subtracting a quantity known from said modulus signal, said quantity representing an audibility threshold value. 
     
     
       6. An audio amplifier circuit as claimed in  claim 5 , comprising a weighting filter block circuit conformed according to a sensitivity of a human ear, said weighting filter block circuit being configured to receive and filter said first input signal and provide a filtered audio signal to said on/off block circuit, said on/off block circuit being configured to generate said off signal if a value of said filtered audio signal is lower than the value of said reference signal. 
     
     
       7. An audio amplifier circuit as claimed in  claim 5 , wherein:
 the on/off block circuit is configured to generate a first gain signal; 
 the processing block circuit includes a gain block circuit configured to receive the first gain signal and said first input signal, and generate a second gain signal; and 
 said gain block circuit is configured to generate said audio signal by multiplying the first input signal by said second gain signal. 
 
     
     
       8. An audio amplifier circuit as claimed in  claim 1 , wherein said processing block circuit is configured to generate the audio signal and provide the audio signal to the first input of said audio power amplifier and set a gain of said audio power amplifier to a minimum value. 
     
     
       9. An audio amplifier circuit as claimed in  claim 8 , wherein said power amplifier is configured to reach said minimum gain value within a period of time ranging from 10 msec to 30 msec, based on the audio signal. 
     
     
       10. An audio amplifier circuit as claimed in  claim 1 , comprising a delay block circuit configured to receive a second input signal and to generate said first input signal as a delayed version of the second input signal. 
     
     
       11. An audio amplifier circuit as claimed in  claim 1 , wherein said sensor comprises a microphone configured to detect said audible sound having said noise component and generate said detected signal. 
     
     
       12. An audio amplifier circuit as claimed in  claim 1 , wherein said sensor comprises an electrical quantity sensor coupled to said audio power amplifier and configured to be coupled to said audio transducer, the electrical quantity sensor being configured to detect said audible sound and generate said detected signal in response to a control signal from said processing block circuit. 
     
     
       13. An audio amplifier circuit as claimed in  claim 1 , comprising an analog-to-digital converter block circuit configured to convert said detected signal into a digital signal. 
     
     
       14. The audio amplifier circuit as claimed in  claim 1  further comprising a loudspeaker coupled to the audio power amplifier, and wherein the audio sensor comprises the loudspeaker. 
     
     
       15. A method, comprising:
 receiving an audio input signal at a first input of a power amplifier; 
 generating an output signal at an output of the power amplifier 
 detecting an audible sound having a noise component, and generating a detected signal based on the audible sound, the detected signal having a noise component corresponding to the noise component of the audible sound; 
 identifying said noise component of said detected signal by processing said detected signal according to said input signal and generating a reference signal; 
 generating an off signal if a value of said input signal is lower than a value of said reference signal; and 
 switching off the power amplifier in response to the off signal. 
 
     
     
       16. A method as claimed in  claim 15 , wherein said generating said off signal includes generating said off signal only if the value of said input signal is lower than the value of said reference signal during a first period of time ranging from 70 msec to 130 msec. 
     
     
       17. A method as claimed in  claim 15 , comprising:
 generating a gain signal; 
 providing the gain signal to said power amplifier; and 
 setting a gain of said power amplifier to a minimum value in response to the gain signal. 
 
     
     
       18. A method as claimed in  claim 17 , wherein setting said gain of said power amplifier comprises reaching said minimum value within a period of time, ranging from 10 msec to 30 msec, after said power amplifier is provided the gain signal. 
     
     
       19. An audio circuit, comprising:
 an audio transducer configured to produce sound; and 
 an audio amplifier circuit configured to provide an output signal to the audio transducer, said audio amplifier circuit including:
 an audio power amplifier having first and second inputs and an output, the audio power amplifier being configured to receive an audio signal at the first input and generate said output signal at the output; 
 an audio sensor configured to detect an audible sound having a noise component, said audio sensor being configured to generate a detected signal having a noise component corresponding to the noise component of the audible sound; and 
 a processing block circuit configured to receive said detected signal, generate an off signal , and provide the off signal to the second input of said audio power amplifier, said processing block circuit being configured to identify said noise component of said detected signal and generate a reference signal by processing said detected signal according to said input signal, said processing block circuit also being configured to generate said off signal when a value of said first input signal is lower than a value of said reference signal. 
 
 
     
     
       20. An audio circuit as claimed in  claim 19 , wherein said processing block circuit comprises an adaptive filter block circuit configured to filter said input signal according to said detected signal, reduce a mean-square error, and generate a filtered signal. 
     
     
       21. An audio circuit as claimed in  claim 20 , wherein said processing block circuit comprises an amplitude determining block circuit configured to receive said filtered signal and generate a modulus signal representative of an amplitude value of said filtered signal. 
     
     
       22. An audio circuit as claimed in  claim 19 , wherein said processing block circuit comprises an on/off block circuit configured to receive said modulus signal generate said off signal and process said reference signal by subtracting a quantity known from said modulus signal, said quantity representing an audibility threshold value. 
     
     
       23. An audio circuit as claimed in  claim 22 , wherein the audio amplifier circuit includes a weighting filter block circuit conformed according to a sensitivity of a human ear, said weighting filter block circuit being configured to receive and filter said first input signal and provide a filtered audio signal to said on/off block circuit, said on/off block circuit being configured to generate said off signal if a value of said filtered audio signal is lower than the value of said reference signal. 
     
     
       24. An audio circuit as claimed in  claim 22 , wherein:
 the on/off block circuit is configured to generate a first gain signal; 
 the processing block circuit includes a gain block circuit configured to receive the first gain signal and said first input signal, and generate a second gain signal; and 
 said gain block circuit is configured to generate said audio signal by multiplying the first input signal by said second gain signal. 
 
     
     
       25. An audio circuit as claimed in  claim 24 , wherein said power amplifier is configured to reach a minimum gain value within a period of time, ranging from 10 msec to 30 msec, from receipt of the off signal. 
     
     
       26. An audio circuit as claimed in  claim 19 , wherein said processing block circuit is configured to generate the audio signal, provide the audio signal to the first input of said audio power amplifier, and set a gain of said audio power amplifier to a minimum value. 
     
     
       27. An audio circuit as claimed in  claim 19 , wherein said sensor comprises an electrical quantity sensor coupled to said audio power amplifier and configured to be coupled to said audio transducer, the electrical quantity sensor being configured to detect said audible sound and generate said detected signal in response to a control signal from said processing block circuit.